Soft vinyl chloride-resins, ethylene/vinyl acetate resins, thermoplastic urethane resins, nylon 12, etc. have hitherto been generally used as materials which give hard rubber-like or leather-like shaped articles. They, however, have certain properties which still require improvements, for example, cold resistance in the soft vinyl chloride resins and nylon 12, abrasion resistance in the ethylene/vinyl acetate resins, and formability in the thermoplastic urethane resins. These properties constitute a setback in exploiting their utility.
As described in JP-B-56-22468 (the term "JP-B" as used herein means an "examined Japanese patent publication"), a polyamide-based elastomer having moderate rigidity and flexibility can be obtained by blending a polyamide resin with an ionic ethylene copolymer. This polyamide-based elastomer has relatively improved cold resistance, particularly impact resistance at low temperatures, in addition to the thermal resistance and abrasion resistance which the polyamide resins inherently possess. However, the above-proposed elastomer is not preferable in that the improvements are still insufficient and that it has poor rubber elasticity because of its high rigidity.
On the other hand, as described in JP-A-55-125153 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), mixtures of polyamide resins and copolymers of ethylene and unsaturated carboxylic acids can be crosslinked by mixing under-heating in the presence of an organic peroxide. However, their impact resistance is still insufficient though it is comparatively improved, and there is a fear of coloration.
JP-A-62-275157 proposes that a thermoplastic resin composition having excellent impact resistance at low temperatures and a well balance between rubber elasticity and rigidity is obtained by melt kneading a polyamide resin with an ethylene/ethyl acrylate/maleic anhydride copolymer, etc.
JP-A-63-146928 describes that a thermoplastic composition having a flexural modulus of from 500 to 15,000 kg/cm.sup.2, which is obtained by melt kneading a polyamide resin with an ethylene/ethyl acrylate/maleic anhydride copolymer, etc. and further melt kneading the resulting blend with a polyfunctional compound such as hexamethylenediamine carbamate, has improved impact resistance, enhanced rigidity, and improved heat distortion resistance due to the incorporation of the polyfunctional compound.
Although each of these compositions has a considerably improved balance of properties, a shaped article which has moderate rigidity with a flexural modulus of from 500 to 15,000 kg/cm.sup.2 so as to be suited for use as various automotive parts, sport shoe soles, etc. and which shows sufficient impact resistance at low temperatures has not yet been obtained. Thus, further improvements have been required.